Apparatus for heating fluids



March 17, 1942. w. THROCKMQRTON "ET AL APPARATUS FOR HEATING FLUIDSFiled May 2, 1941 .2 Sheets-Sheet l INVENTORS. (Jo/7x7 l M ThracKMafl/ar.

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March 17, 1942- J. w. THROCKMORTON ET AL 2,276,528

APPARATUS FOR HEATING FLUIDS INVENTORS.

ATTORNEY.

Patented Mar. 17, 1942 APPARATUS FOR. HEATING FLUIDS John W.Throckmorton, Wilton, and John S. Wallis, Darien, Conn., assignors toPetro-Chem Development Compan poration of Delaware y, New York, N. Y., acor- Application May 2, 1941, Serial No. 391,522

2 Claims.

Our invention relates to afurnace construction for heating fluids andmore particularly to a tubular furnace in which the heat exchangeelements or tubes are verticallyipositioned in a combustion chamberaround the perimeter of a circle and the combustion gases circulatedover the tubes and through the combustion chamber to transfer relativelyuniform radiant and convection heat to the tubes throughout theirlengths.

The furnace is adaptable for use in any connection Where fluids are tobe heated, as for instance the chemical industry for processinganddistillation, and in the oil ind try for distillation, cracking and forother ty s of thermal processing as well as boilers and steamgeneration. 1

This invention is an improvement over the furnace shown in our copendingapplications, Serial No. 343,272, filed June 29, 1940, and Serial No.384,892, filed March 24, 1941.

One object of our invention is to provide a furnace in which uniformheat intensity is distributed throughout the full length of all of theheat exchange elements or tubes.

Another object is to provide a furnace of high efliciency in-whichradiant heat is uniformly supplied to the lower portions of the tubesand convection heat to the upper portions of the tubes.

A further object of the invention is to provide a furnace setting inwhich a plurality ,of heating elements such as tubes are arranged in thesetting and fired'in such a. manner that uniform heat distribution isobtained circumferentially and longitudinally of the tubes.

Another object of our invention is to provide radiant reflectingsurfaces and sources of combustion gases outside of the heat exchangeelements which will supplement the radiant heat furnished from thecombustion gases inside of the heat exchange elements todistribute'radiant' heat more uniformly over the entire heat transfersurfaces of the tubes or heat exchange elemerits.

Other and further objects of our invention will appear from thefollowing description.

In the accompanying drawings which form part of the instantspecification and are to be read in conjunction therewith and in whichlike reference numerals are used to indicate like parts in the variousviews;

Fig. 1 is a sectional view of a furnace showing one embodiment of ourinvention.

Fig. 2 is a view-taken along the line 2-2 in Fig. 1.

Figs. 3, 4, 5, and 6 are half sections" showing.

modifications of the construction shown in Fig. 1.

Referring to the drawings, supported on a concrete base is a pedestal Iwhich carries tube supports 2 and a prefabricated metal sheathing. 3. Aninternal alloy sheathing 4 is spaced from the sheathing 3 and'betweenthe outer casing 3 and inner reflecting surface '4 is insulation 5.

While an internal alloy sheathing 4 is shown as in our previouscopending applications, when utilizing the double firing both inside andoutside of the tube circle the alloy sheathing may be dis- Y pensed withand the conventional type of refractory setting used. This insulatingmaterial is preferably mono-block, high temperature, or may be arrangedinlayers with rcck wool blanket or the like. Vertically positionedwithin the combustion chamber 6 are a plurality of vertical heatexchange elements or tubes 1 arranged around the perimeter of acircle-within the combustion chamber and held in place at their upperextremities by a U-shaped channelm which renders accessible theremovable return bend connections shown at 9. Similar return bend.con-

nections are available through the tube supports 2 at the lower ends ofthe tubes. At the bottom and positioned centrally of the combustionchamber is a combustion pct 10 in which are located burners ll. Theseburners are preferably 6 arranged tangentially of the combustion pot andThe flow of combustion gases is may be of the directional type'so thatthe combustion heating gases produced from the burning of: liquid orgaseous fuel can be directed into the combustion chamber according tothe direction: in which the burners are arranged. These burners llfurnish the heating gases to the combustion space inside of the circleof tubular heating elements. Outside of the heating elements and withinthe space 6 are burners l2 extending rise and join the combustion gasesfrom burners II in a constricted passageway between the cone l4 and theupper truncatedcone section of the combustion chamber adjacent theconical -refleeting baflle. The cone I4 is ofalloy metal or otherreflective material including refractories and is supported from theinverted funnel-shaped flue l5 by" rods l6, fastened to the base of thecone and to supports l1 arranged around the inside of the flue. Theinverted funnel-shaped flue 16 has, mounted at its top, a chimney orstack l8. The lower base of the flue I5 is supported upon the channel 8through which the ends of the heating tubes extend. Into the base of theflue l5 rises a cylindrical throat of insulating material l9, which hasa widened base to collect the combustion gases passing around the baseof the reflecting cone l4 and direct them into the flue l5 and to stackl8.

In the modification shown in Fig. 3, combustion gases are generatedwithin the combustion pot I0 by burners II in a similar manner to thatshown in Fig. 1. The combustion chamber, however, is somewhatdifferently shaped, being tapered both at the top and bottom and firedoutside of the tube near a central position at burners l3. The remainderof the construction is substantially identical to that explained inconnection with Fig. l with the exception that the reflecting cone I4 issomewhat larger in order to supply a larger reflecting surface.

The modification shown in Fig. 4, in so far as the combustion chamber isconcerned, is similar to that shown in Fig. l, the space 6 outside ofthe tubes being fired by burners l2 and I3, and the combustion spacewithin the tubes fired by burners II within the combustion pot In. Inthis modification, however, the conical baflie or reflecting cone l4 hasa cylindrical portion Ma at its base which produces a considerablylonger restricted passage between the cylindrical portion of the coneand the upper cylindrical portion of the combustion chamber. In thismodification also there are two rows or banks of tubes 1 in place of thesingle row shown in Figs. 1 and 3.

The modification shown in Fig. 5 is similar to that shown in Fig. 4,except that the inner bank of tubes adjacent the reflecting cone M aresomewhat longer than the outer bank of tubes. This outer bank of tubesreceivesradiant heat from the combustion gases emitted from burners l2and I3 and the reflecting wall of the combustion chamber. The long tubeswhich constitute the inner bank receive radiant heat from combustiontaking place in combustion pot I0 from gases produced by fuel consumedin burners II. In Fig. 1 and in the modifications shown in Figs. 3, 4,and 5, the burners H and I3 are tangentially arranged, while burners I2are of the directional type, discharging the gases at an angle towardthe outer surface of the heat exchange elements.

'In Fig. 6, the combustion chamber, tube banks and reflecting cone aresimilar to the construction shown in Fig. 5. Burners l3 are arrangedtangentially of the combustion chamber and centrally thereof, while theburners through the bottom of the chamber, II and I2, are arranged tosupply heat inside and outside of the combustion chamber similarly tothe previous figures except that burners II are raised to the floor ofthe chamber as the combustion pot It has been eliminated. The designeliminating the ignition or combustion pot I may be applied as well tothe proceeding modifications, if desired.

The modification shown in Fig. 6, in which' a baflie wall 20 is used,offers a design in which two separate heating circuits are mounted inthe same furnace setting and have controlled heat supply to eachcircuit. Such conditions arise in the cracking of petroleum where theheating and soaking circuits require variable heat loads; also in twostage distillation, different amounts of heat are required for theseparate stages. By varying the firing of burners l2 and I3 outside thebafile wall 20 with respect to the firing of burners ll inside thebailie wall, the above desired variance of heat load and controlledconditions of heat supplied to each circuit is obtained.

The tapering of the top of the combustion chamber in the form of atruncated cone and the inverted baffle cone offer reflecting surfacesfor radiant heat generated in the spaces inside and outside of the tubesand direct this radiant heat more uniformly upon the upper portion ofthe tubes. The shape of the combustion chamber and the baflle cone alsoserve to constrict the passageway through which the combustion gasesflow from inside and outside of the tubes to the flue, increasing thevelocity of the gases as their temperature decreases, thus obtaining abetter heat exchange upon the upper portions of the tubes. The burnersII and I3 are arranged tangentially as shown in Figs. 1 to 5 inclusive,to give the gases a whirling motion, both inside and outside of the tubebanks. The reflected or radiant heat from both the cone and thecylindrical and conical surfaces of the combustion chamber, as well asfrom both sides of the cylindrical wall 20 in Fig. 6, distributes evenlyover the lower portions of the heating elements radiant heat generatedinside and outside of the tube banks. The convection heat suppliedprincipally to the upper portions of the tubes is concentrated and thevelocity of the gases increased by restricting the passageway throughwhich the gases must pass from the combustion chamber to the flue.

In the modifications shown in Figs. 4, 5, and 6, where a shortconvection zone exists between the combustion chamber and flue, it iscontemplated that extended surfaces such as fins may be used on thetubes to distribute more uniformly the convection heat of the combustiongases.

By the use of such a convection zone in the upper part of the combustionor heating chamber, it maybe unnecessary to use brickwork in the top ofthe furnace, because the flue gasis sufiiciently low in temperature tobe introduced directly into the stack. By the construction shown in Fig.l, and the subsequent modifications, there is provided a furnace of-highefliciency wherein the heat of the combustion gases is distributed asradiant and convection heat throughout the full-length of the tubes, allof the tube surfaces operating at the maximum possible heat transferrate. The interior of the tubes is rendered accessible for cleaning bysuitable cleanout connections at the top and bottom, and theconstruction is such that it lends itself easily to replacement orrepairs of either the tubes or combustion chamber.

Observation ports may be placed at convenient locations in order thatthe operators can at all times determine conditions within the furnace.

It will be undersood that certain features and sub-combinations are ofutility and may be employ-ed without reference to other features andsub-combinations. This is contemplated by and is within the scope of ourclaims. It is further obvious that various changes may be made indetails within the scope of our claims without departing from the spiritof our invention. It is, therefore, to be understood that our inventionis not to be limited to the specific details shown and described.

Having thus described our invention, we claim: 1. A furnace including incombination a combustion chamber of circular cross section, the

upper portion simulatingv a truncated cone, av

plurality of vertically disposed heat exchange elements positioned insaid combustion chamber and substantially around the perimeter of acircie, means positioned within said combustion chamber within saidspace surrounded by said heat exchange elements and located in thatportion of the combustion chamber simulating a truncated cone having theform of a. cone with its apex depending, said cone and truncated por-'tion or the combustion chamber adapted to progressively decrease thecross sectional area of the upper part of said combustion chamber, andseparate sources of combustion heating gases positioned inside andoutside of the circle of heat exchange elements.

2. A furnace including in combination a combustion chamber or circularcross section, the upper portion simulating a truncated cone, a plu-'rallty of substantially vertical heat exchange elements positioned in'said combustion-chamber and substantially around the perimeter of acircle, means positioned within said combustion chamber within saidspace surrounded by said heat exchange elements and located in thatportion of the combustion chamber simulating a truncated cone having theform of a cone with its apex depending, said cone and truncated portionof the combustion chamber adapted-to progressively decrease the crosssectional area of the upper part of said combustion chamber, and

separate sources of combustion -heating gases positioned inside andoutside of the circle of heat exchange elements and'tangentiaily in thecombustion chamber wall adjacent its mid-section. JOHN W. THROCKMORTON.

JOHN S. WALLIS.

